JEE Advanced levelSingle correct optionDifficulty 3 of 3pb215
6.85 g of red lead, PbX3OX4, is treated with excess dilute nitric acid. The brown residue is PbOX2 (PbX3OX4+4HNOX32Pb(NOX3)X2+PbOX2+2HX2O). With Pb = 207 and O = 16, the mass of PbOX2 obtained is
A2.39 g
B7.17 g
C2.07 g
D4.78 g
Answer: A
Molar mass of PbX3OX4 = 3(207) + 4(16) = 685 g/mol, so moles = 6.85/685 = 0.01 mol. Each mole yields one mole of PbOX2 (239 g/mol), so mass = 0.01 x 239 = 2.39 g.